British cyclist David Millar has strongly criticised former friend Lance Armstrong - claiming he can see 'no happy ending' from the current investigation into the American's alleged doping.

Millar - who himself served a two-year ban from 2004 after testing positive for EPO - believes the increasingly ugly probe into the seven-time Tour de France winner is bringing nothing but bad publicity to the sport, and has overshadowed a lot of good progess that has been made.

However, he accepts that the investigation from the US Food & Drug Administration is the best way to get to the bottom of whatever really went on.

"The entire Lance thing - did he dope or didn't he dope - is suffocating the sport and obscuring a lot of good developments," Millar said, while speaking at the release of his autobiography.

"The only resolution is to let the FDA investigation take its full course and for that to be the final word on the matter.

"Whatever the eventual outcome - and I'm struggling to see a happy ending - we have to accept the verdict collectively and move on. That would offer some sort of closure and we can call a halt to the endless process and draining debate.

"We have to end it and the FDA are the best qualified to do the definitive investigation.

"In fact cycling has always been 'saved' by judicial investigations and not by the anti-doping controls we put in place. That's the harsh truth. We have relied on them to clean the sport up."

Despite that, Millar cannot say for certain whether the accusations against Armstrong have merit. He wonders why the American never really chose to stand up against doping while his influence was at its highest, however.

"I can't say definitively if Lance doped or not," he added. "Yes, there are all the stories and rumours but I certainly never saw him dope with my own eyes.

"If he did dope, after all he has said and done, it would be unforgivable. His performances on the Tour were extraordinary but he is unlike anybody you will ever meet. He is a force of nature.

"But I have always thought that he could have done more against doping. He was in a position to make a difference and to help his sport but I never saw any evidence of that."

Millar is less critical of Alberto Contador, however, the three-time Tour de France winner who has seen his own case over a failed drugs test move to the European Court of Arbitration for Sport.

"Alberto is untouchable as a rider, a physical freak, and we in the peloton have known that for a long time," he said. "I would be very surprised if he didn't end up as the greatest Grand Tour rider ever.

"It's a tragedy that he has got mixed up in this clenbuterol thing but I am keeping an open mind on his case."